Nitrogen and Sulfur Co-doped Carbon Dots as a Turn-Off Fluorescence Probe for the Detection of Cerium and Iron.

Carbon dots has becoming one of the most promising fluorescence sensors to determine the trace level of heavy metals in environments because of their advantages in optical properties, response time, and convenient operation procedures. Herein, a novel nitrogen and sulfur co-doped carbon dots (NS-CDs) were prepared though microwave assisted approach using DL-malic acid and allyl thiourea for the first time. Due to the existence of nitrogen and sulfur, the as-prepared NS-CDs exhibited bright blue fluorescence at 430 nm upon 330 nm excitation, with a fluorescence quantum yield of 19.8%. The sensitivity study of NS-CDs against metal ions and organic molecules has approved that the fluorescence could be further quenched by Ce4+ and Fe3+ ions, with the same linear detection ranges varying from 10 to 90 µM. The limits of detection (LOD) were determined as low as 0.75 µM and 0.67 µM for Ce4+ and Fe3+ ions, respectively. The possible quenching mechanism is explained by inner filter effect and static quenching mechanism for Ce4+ ions, while the quenching effect caused by Fe3+ ions is attributed to the inner filter effect, static and dynamic quenching mechanisms. Additionally, the developed sensor was used for the detection of Ce4+ and Fe3+ ions in tap water with satisfactory recoveries. Finally, the designed NS-CDs sensor possesses good biocompatibility against MA104 cells, suggesting the sensor can be potentially applied to detect Ce4+ and Fe3+ ions in environment and biological systems.

Leaf spot of Alnus cremastogyne Caused by Colletotrichum gloeosporioides in Sichuan, China.

Alnus cremastogyne Burk, a broad-leaved tree endemic to south-western China, has both ecological and economic value. The tree is widely used in furniture, timber, windbreaks and sand fixation, and soil and water conservation (Tariq et al. 2018). In December 2020, a new leaf spot disease was discovered on A. cremastogyne in two plant nurseries in Bazhong City (31°15' to 32°45N, 106°21' to 107°45'E), with 77.53% disease incidence. Among the infected trees, 69.54% of the leaves were covered with symptoms of the disease. The typical symptoms initially appeared as irregular brown necrotic lesions, while some lesions were surrounded by a light yellow halo. As the disease progressed, the number of necrotic lesions increased, and lesions gradually expanded and coalesced (Fig. 1). Finally, the disease caused the leaves of A. cremastogyne to wither, curl, die, and fall off. Ten symptomatic leaves were collected from 5 different trees in the two plant nurseries. The leaves with symptoms of leaf spot disease were collected and cut from the junction between the diseased and the healthy tissues. The infected tissues from 10 samples were cut into small 2.5 × 2.5 mm pieces. Infected tissues was sterilized in 3% NaClO solution for 60 s followed by 75% ethanol for 90 s, rinsed three times in sterile water, blot-dried with autoclaved paper towels, and then cultured on potato dextrose agar (PDA) at 25℃ for 4 to 8 days in 12 h/12 h light/dark conditions. After 8 days, the colony diameter reached 71.2 to 79.8 mm. The colonies were initially light pink, and then turned white with pale orange beneath. The conidia were single-celled, aseptate, colorless, cylindrical, straight, bluntly rounded at both ends, and measured 11.6 to 15.9 × 4.3 to 6.1 µm (n = 100). These morphological characteristics were consistent with the description of Colletotrichum gloeosporioides (Pan et al. 2021). For molecular identification, the genomic DNA of a representative isolate, QM202012, was extracted using a fungal genomic DNA extraction kit (Solarbio, Beijing). The internal transcribed spacer (ITS), actin (ACT), and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) genes were amplified with primers ITS1/ITS4 (White et al. 1990), ACT-512F/ACT-783R (Carbone & Kohn, 1999) and GDF/GDR (Templeton et al. 1992), respectively. Sequences were deposited in GenBank (ITS: OL744612, ACT: OL763390, and GAPDH: OL799166). BLAST results indicated that the ITS, ACT, and GAPDH sequences showed >99% identity with C. gloeosporioides sequences in NCBI (GenBank NR160754, MG561657, and KP145407). Identification was confirmed by Bayesian inference using Mr Bayer (Fig 2) A conidial suspension (1 × 106 conidia/ml) was used to test pathogenicity on the leaves of 4-year-old A. cremastogyne plants (10 plants). Fifteen leaves of each plant (10 pots in total) were inoculated with the spore suspension on the leaves. The same number of control leaves was sprayed with sterilized distilled water as a control. Finally, all potted plants were placed in a greenhouse at 25°C under 16 h/8 h photoperiod and 67 to 78% relative humidity. The symptoms observed on the inoculated plants were similar to those of the original diseased plants, with 100% of the inoculated plants being infested with brown leaf spots, but the controls remained symptom-free. C. gloeosporioides was re-isolated from the infected leaves and identified by both morphological characteristics and DNA sequence analysis. The pathogenicity test was repeated three times, showing similar results each time, confirming Koch's postulates. To our knowledge, this is the first report of leaf spot on A. cremastogyne caused by C. gloeosporioides in China. This finding indicates that C. gloeosporioides may become a serious threat to A. cremastogyne production in Bazhong City and helps to further examine and prevent leaf spot disease in A. cremastogyne growing areas in Bazhong City.

A universal growth strategy for DNA-programmed quantum dots on graphene oxide surfaces.

The emerging materials of semiconductor quantum dots/graphene oxide (QDs/GO) hybrid composites have recently attracted intensive attention in materials science and technology due to their potential applications in electronic and photonic devices. Here, a simple and universal strategy to produce DNA-programmed semiconductor quantum dots/graphene oxide (QDs/GO) hybrid composites with controllable sizes, shapes, compositions, and surface properties is reported. This proof-of-concept work successfully demonstrates the use of sulfhydryl modified single-stranded DNA (S-ssDNA) as a 'universal glue' which can adsorb onto GO easily and provide the growth sites to synthesize CdS QDs, CdSe QDs, CdTe QDs and CdTeSe QDs with distinctive sizes, shapes and properties. Also, adapting this method, other graphene oxide-based hybrid materials which are easily synthesized in aqueous solution, including oxides, core-shell structure QDs and metal nanocrystals, would be possible. This method provided a universal strategy for the synthesis and functional realization of graphene -based nanomaterials.

Theoretical Insight into the Mechanisms and Regioselectivity of [4 + 3] and [4 + 1] Annulations of Enals with Azoalkenes Catalyzed by N-Heterocyclic Carbenes.

The reaction mechanisms on the NHC-catalyzed [4 + 3] and [4 + 1] annulations of enals with azoalkenes have been theoretically investigated with the aid of the density functional theory calculations. It is found that the additives play an important role in promoting proton transfer and dehydration. The impacts of catalysts (NHC-A and NHC-B) and substituent groups on the regioselectivity were rationalized. The origin of the regioselectivity involved in these reactions was probed by performing distortion-interaction analysis. For reaction A with NHC-A as the catalyst and Boc group as the substituent, the regioselectivity is predicted to be determined by the interaction energy of 3 with R2' in TS3A versus TS8A. For reaction B with NHC-B as the catalyst and Boc group as the substituent, the unstable boat-type conformation versus the stable chair-type conformation involved in the NHC-B moiety accounts for the regioselectivity. In reaction C with NHC-A as the catalyst and Ts group as the substituent, distortion energies of 3 and R2' in TS3C versus TS6C are found to be the major reason delivering regioselectivity even higher than that of reaction A.

Theoretical investigation on the chemoselective N-heterocyclic carbene-catalyzed cross-benzoin reactions.

A density functional theory study was performed to understand the detailed mechanisms of the cross-benzoin reactions catalyzed by N-heterocyclic carbene (NHC) species. Our theoretical study predicted that the first H-transfer operates with water in solution as a mediator, and the second H-transfer undergoes a concerted mechanism rather than a stepwise one. In addition, the chemoselectivity of the reactions studied in this work has been explored. P1 was obtained as a major product mainly due to the more stable intermediate formed by reaction of NHC with reactant R1. Different steric effects resulting from the fused six-membered ring in transition state TS7 and the fused five-membered ring in transition state TS13 are the origin leading to the chemoselectivity.

The effect of carbon-polyaniline hybrid coating on high-temperature electrochemical performance of perovskite-type oxide LaFeO3 for MH-Ni batteries.

An efficient carbon-polyaniline (PANI)-coated method was applied for perovskite-type oxide LaFeO3 to enhance its high-temperature electrochemical performance. Transmission electron microscopy (TEM) results reveal that LaFeO3 particles are evenly coated with carbon and PANI hybrid layers after carbon-PANI treatment. The carbon layers prevent the nanosized LaFeO3 particles from aggregation and allow the electrolyte to penetrate in every direction inside the particles. The PANI layers also enhance the electrocatalytic activity, facilitating hydrogen protons transferring from the electrolyte to the electrode interface. The cooperation of carbon and PANI hybrid layers results in a significant enhancement of the electrochemical performance at high temperatures. At an elevated temperature (60 °C), the maximum discharge capacity of the LaFeO3 electrodes remarkably increases from 231 mA h g(-1) to 402 mA h g(-1) and the high rate dischargeability at a discharge current density of 1500 mA g(-1) (HRD1500) increases from 22.7% to 44.3%. Moreover, the hybrid layers mitigate the corrosion of LaFeO3 electrodes by reducing the loss of active materials in the alkaline electrolyte, leading to increase in the capacity retention rate from 67.1% to 77.6% after 100 cycles (S100).

The photoluminescence properties of CdSe QDs prepared by the one-pot process.

CdSe quatum dots (QDs) have been prepared through the one-pot process. Ultraviolet-visible (UV-vis) absorption and emission spectra were used to characterize the resulting samples. The effect of the synthesis time and temperature on the optical properties of the CdSe QDs samples have been studied. The maximum of the absorption spectra of the CdSe QDs samples is 486 nm and the emission spectra is 528 nm. The emission intensity of the CdSe QDs samples increases, and the emission maximum presents a red shift with increasing reaction time.

Reversible Insertion of [AlCl4 ]- Superhalides in Graphite.

Graphite-based dual-ion batteries are with potential higher energy density, making them a unique candidate in energy storage systems. However, anion insertion into graphite in aqueous environment remains a significant challenge. Herein, we report that the reversible insertion of Al-Cl superhalide into expanded graphite (EG) delivers an ultrahigh specific capacity of ~171 mAh g-1 from an aqueous deep eutectic solvent (DES) gel electrolyte of 50 m ChCl+5 m AlCl3 . High-resolution transmission electron microscopy (HRTEM), Raman spectra and X-ray diffraction (XRD) show that the EG generates turbostratic structure during Al-Cl superhalide (de)insertion instead of presenting typical graphite intercalation compounds (GIC), thus attributing to the high capacity during Al-Cl superhalide insertion.

V-doped activated Ru/Ti2.5V0.5C2 dual-active center accelerate hydrogen production from ammonia borane.

Designing and constructing the active center of Ru-based catalysts is the key to efficient hydrolysis of ammonia borane (NH3BH3, AB) for hydrogen production. Herein, V-doped Ru/Ti2.5V0.5C2 dual-active center catalysts were synthesized, showing excellent catalytic ability for AB hydrolysis. The corresponding turnover frequency value was 1072 min-1 at 298 K, and the hydrolysis rate rB of AB was 235 × 103 mL·min-1·gRu-1. X-ray photoelectron spectroscopy results indicated that the interaction between V-doped Ti3C2 and catalytic metal Ru transfers electrons from Ti to Ru, resulting in electron-rich Ru species. According to density functional theory calculations, the activation energy and reaction dissociation energy of the reactants AB and H2O on V-doped catalysts were lower than those of Ru/Ti3C2, thus optimizing the catalytic kinetics of AB hydrolysis. The modification strategy of V-doped Ti3C2 provides a new pathway for the development of high-performance catalysts for AB hydrolysis.

Evaluation of anomalies in GLDAS-1996 dataset.

Global Land Data Assimilation System (GLDAS) data are widely used for land-surface flux simulations. Therefore, the simulation accuracy using GLDAS dataset is largely contingent upon the accuracy of the GLDAS dataset. It is found that GLDAS land-surface model simulated runoff exhibits strong anomalies for 1996. These anomalies are investigated by evaluating four GLDAS meteorological forcing data (precipitation, air temperature, downward shortwave radiation and downward longwave radiation) in six large basins across the world (Danube, Mississippi, Yangtze, Congo, Amazon and Murray-Darling basins). Precipitation data from the Global Precipitation Climatology Centre (GPCC) are also compared with GLDAS forcing precipitation data. Large errors and lack of monthly variability in GLDAS-1996 precipitation data are the main sources for the anomalies in the simulated runoff. The impact of the precipitation data on simulated runoff for 1996 is investigated with the Community Atmosphere Biosphere Land Exchange (CABLE) land-surface model in the Yangtze basin, for which area high-quality local precipitation data are obtained from the China Meteorological Administration (CMA). The CABLE model is driven by GLDAS daily precipitation data and CMA daily precipitation, respectively. The simulated daily and monthly runoffs obtained from CMA data are noticeably better than those obtained from GLDAS data, suggesting that GLDAS-1996 precipitation data are not so reliable for land-surface flux simulations.

L-Theanine attenuates heat stress-induced proteotoxicity and alterations in carbohydrate and lipid metabolism via heat shock factor 1.

Extreme heat caused by global warming accelerated the frequency of heat stress (HS). Proteotoxic stress induced by the aggregation of misfolded proteins and metabolic stress triggered by alterations in the metabolism were observed during HS. The activation of heat shock factor 1 (Hsf1) and its interaction with adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) are critical in addressing proteotoxicity and metabolic stress in heat-stressed organisms. Previous studies have shown that L-theanine (LTA) can regulate nutrient metabolism through the AMPK pathway and can alleviate HS. Therefore, we hypothesize that LTA may help in restoring homeostasis by regulating nutrient metabolism under HS. Here, we investigated the effects of LTA on nutrient metabolism in heat-stressed rats and characterized the underlying mechanisms using RNA sequencing and metabonomics. The results showed that LTA alleviated HS-induced liver damage, promoted body weight gain, decreased serum cortisol and enhanced the total protein content. Besides, it regulated the expression of genes related to carbohydrate, lipid and amino acid metabolism and altered metabolite levels. Moreover, LTA inhibited the expression of Hsf1 and heat shock protein 70 (Hsp70), promoted AMPK phosphorylation and the expression of glucose-6-phosphatase catalytic subunit 1 (G6pc), and inhibited the phosphorylation of acetyl-CoA carboxylase 1 (ACC1) in heat-stressed rats. Mechanistically, LTA alleviated HS-induced proteotoxic stress by acting on Hsf1/Hsp70; simultaneously, it promoted AMPK phosphorylation by suppressing Hsf1 expression, which in turn inhibited fatty acid synthesis and hepatic gluconeogenesis, thus alleviating HS-induced metabolic stress. These results suggest that LTA regulates nutrient metabolism through Hsf1/AMPK and alleviates HS-induced proteotoxicity via Hsf1/Hsp70.

L-Theanine alleviates heat stress-induced impairment of immune function by regulating the p38 MAPK signalling pathway in mice.

With the current trend of global warming, heat stress-induced impairment could seriously endanger human health. L-Theanine is a non-protein amino acid in tea with various biological activities, including immunoregulatory, anti-anxiety, and anti-oxidation. However, its effect on immune function under heat stress and the underlying mechanism are currently unclear. In this study, male BALB/c mice were used as experimental objects to explore the effect of L-theanine on heat stress-induced changes in immune function and its mechanism. Three doses of L-theanine were used: low (100 mg kg-1 d-1), medium (200 mg kg-1 d-1), and high (400 mg kg-1 d-1). Treatment with L-theanine could attenuate the heat stress-induced reductions in body weight and feed intake in mice, alleviate damage in the liver and jejunum, and inhibit the inflammatory factors IL-6, IL-1ß, and TNF-α. Aspartate aminotransferase and alanine transaminase activity levels and the malondialdehyde content decreased, while the IgA, IgM, and IgG contents increased in response to L-theanine. It is possible that L-theanine affects the P38 signalling pathway and inhibits the increase in p-P65/P65 caused by the overexpression of HSP27 and regulation of PPAR-γ and Foxp3 proteins, thereby alleviating immune dysfunction caused by heat stress.

Hydro-economic model framework for achieving groundwater, food, and economy trade-offs by optimizing crop patterns.

When allocating water resources, stakeholders (such as water departments, agricultural sector actors, and farmers) aim to maximize their benefits. This leads to conflicts between water savings, food security, and profit growth, causing major challenges for water managers. A hydro-economic model was developed to alleviate groundwater sustainability, food security, and economic growth (GFE) conflicts through crop pattern optimization. This model combines groundwater, agronomic, and economic sub-models to simulate spatiotemporal variations in groundwater level, irrigation requirement, crop production, and net profit. The NSGA-II algorithm was used to maximize net profits while minimizing groundwater extraction and food reduction through crop pattern optimization in irrigation areas and under crop production constraints. Then, using the Baoding Plain as the study area, three scenarios with no external water supply and nine scenarios with an external water supply of 0.3, 0.6, and 0.9 km3/y were designed. The present crop pattern caused a groundwater decline of 0.32 m/y and an overdraft of 0.61 km3/y. The three scenarios without external water supply showed different options for maximizing net profit, minimizing groundwater extraction, and minimizing food reduction without affecting food production, food self-sufficiency or groundwater sustainability. All three scenarios cannot simultaneously satisfy the GFE target. With an external water supply of 0.3 km3/y, only one scenario met the GFE target; with that of 0.6 km3/y, all scenarios met the GFE target; and with that of 0.9 km3/y, groundwater levels increased, profits overflowed, and food overproduction occurred.

An aqueous copper battery enabled by Cu2+/Cu+ and Cu3+/Cu2+ redox conversion chemistry.

We propose an aqueous copper battery via Cu2+/Cu+ and Cu3+/Cu2+ redox conversion chemistry on an activated carbon (AC) electrode enabled by a 30 m ChCl + 1 m CuCl2 electrolyte, where Cu3+/Cu2+ redox promotes the discharge capacity by ∼50 mA h g-1 at ∼1.0 V vs. Ag/AgCl with stable cycling.

Learning From Large-Scale Noisy Web Data With Ubiquitous Reweighting for Image Classification.

Many important advances of deep learning techniques have originated from the efforts of addressing the image classification task on large-scale datasets. However, the construction of clean datasets is costly and time-consuming since the Internet is overwhelmed by noisy images with inadequate and inaccurate tags. In this paper, we propose a Ubiquitous Reweighting Network (URNet) that can learn an image classification model from noisy web data. By observing the web data, we find that there are five key challenges, i.e., imbalanced class sizes, high intra-classes diversity and inter-class similarity, imprecise instances, insufficient representative instances, and ambiguous class labels. With these challenges in mind, we assume every training instance has the potential to contribute positively by alleviating the data bias and noise via reweighting the influence of each instance according to different class sizes, large instance clusters, its confidence, small instance bags, and the labels. In this manner, the influence of bias and noise in the data can be gradually alleviated, leading to the steadily improving performance of URNet. Experimental results in the WebVision 2018 challenge with 16 million noisy training images from 5000 classes show that our approach outperforms state-of-the-art models and ranks first place in the image classification task.

Quantifying the magnitude of the impact of climate change and human activity on runoff decline in Mian River Basin, China.

Runoff in North China has been dramatically declining in recent decades. Although climate change and human activity have been recognized as the primary driving factors, the magnitude of impact of each of the above factors on runoff decline is still not entirely clear. In this study, Mian River Basin (a watershed that is heavily influenced by human activity) was used as a proxy to quantify the contributions of human and climate to runoff decline in North China. SWAT (Soil and Water Assessment Tool) model was used to isolate the possible impacts of man and climate. SWAT simulations suggest that while climate change accounts for only 23.89% of total decline in mean annual runoff, human activity accounts for the larger 76.11% in the basin. The gap between the simulated and measured runoff has been widening since 1978, which can only be explained in terms of increasing human activity in the region. Furthermore, comparisons of similar annual precipitation in 3 dry-years and 3 wet-years representing hydrological processes in the 1970s, 1980s, and 1990s were used to isolate the magnitude of runoff decline under similar annual precipitations. The results clearly show that human activity, rather than climate, is the main driving factor of runoff decline in the basin.

Dimethyl-ammonium diaqua-(pyridine-2,4-dicarboxyl-ato-κN,O)cuprate(II).

The asymmetric unit of the title compound, (C(2)H(8)N)(2)[Cu(C(7)H(3)NO(4))(2)(H(2)O)(2)], contains one-half of a mononuclear [Cu(C(7)H(3)NO(4))(2)(H(2)O)(2)](2-) anion, one dimethyl-ammonium cation and one aqua ligand. The Cu(II) atom, lying on an inversion center, is coordinated by two symmetry-related N atoms and two O atoms from one pyridine-2,4-dicarboxyl-ate ligand and two symmetry-related aqua ligands and exhibits a distorted octa-hedral trans-[CuN(2)O(4)] coordination geometry. Multiple crystallographically independent O-H⋯O and N-H⋯O hydrogen bonds form a three-dimensional network in the crystal structure.

catena-Poly[copper(II)-bis-(µ-3-cyano-2-hydroxy-propionato)-κN:O,O;κO,O:N-copper(II)].

The title compound, [Cu(C(4)H(4)NO(3))(2)](n), exhibits a double-chain structure extending along [100]. The Cu(II) atom, lying on an inversion center, is coordinated by two cyano N atoms from two 3-cyano-2-hydroxy-propionate ligands and two hydr-oxy O atoms and two carboxyl-ate O atom from two other two ligands in a distorted octa-hedral geometry. Inter-molecular C-H⋯O and O-H⋯O hydrogen bonds connect the chains into a three-dimensional structure.

Improved hydrogen storage properties of MgH2 by nickel@nitrogen-doped carbon spheres.

Magnesium hydride is considered to be one of the most desirable hydrogen storage materials due to its high weight capacity (7.6 wt% H2) and low price. However, its relatively high operating temperatures and slow dynamics have always hampered its commercial applications. In this paper, nano-nickel particle coated nitrogen-doped carbon spheres (Ni@NCS) were synthesized by a chemical reduction method and then introduced into Mg to form an MgH2-Ni@NCS composite via hydriding combustion and subsequent high-energy ball milling processes. The results showed that the MgH2-Ni@NCS composite possessed high hydrogen storage capacity and fast absorbing/desorbing kinetics, absorbing 5.7 wt% H2 and desorbing 4.3 wt% H2 within 8 min at 623 K. Moreover, the capacity shows negligible degradation after 10 cycles, indicating that the MgH2-Ni@NCS composite has good cycling stability. Even at relatively low temperature (373 K), the MgH2-Ni@NCS composite still absorbed 4.2 wt% H2 within 60 min compared to 0.9 wt% H2 for milled MgH2. The improvement in hydrogen storage properties is ascribed to the in situ formed Mg2NiH4 induced dehydrogenation of MgH2 and effective prevention of the agglomeration of magnesium during the hydriding/dehydriding reaction by the carbon material.

Using runoff slope-break to determine dominate factors of runoff decline in Hutuo River Basin, North China.

Water resources in North China have declined sharply in recent years. Low runoff (especially in the mountain areas) has been identified as the main factor. Hutuo River Basin (HRB), a typical up-stream basin in North China with two subcatchments (Ye and Hutuo River Catchments), was investigated in this study. Mann-Kendall test was used to determine the general trend of precipitation and runoff for 1960-1999. Then Sequential Mann-Kendall test was used to establish runoff slope-break from which the beginning point of sharp decline in runoff was determined. Finally, regression analysis was done to illustrate runoff decline via comparison of precipitation-runoff correlation for the period prior to and after sharp runoff decline. This was further verified by analysis of rainy season peak runoff flows. The results are as follows: (1) annual runoff decline in the basin is significant while that of precipitation is insignificant at alpha=0.05 confidence level; (2) sharp decline in runoff in Ye River Catchment (YRC) occurred in 1968 while that in Hutuo River Catchment (HRC) occurred in 1978; (3) based on the regression analysis, human activity has the highest impact on runoff decline in the basin. As runoff slope-breaks in both Catchments strongly coincided with increase in agricultural activity, agricultural water use is considered the dominate factor of runoff decline in the study area.